Generally, the peripheral input device of a computer includes for example a mouse device, a keyboard device or a trackball device. Via the keyboard device, the user may input characters and symbols into the computer. As a consequence, most users and most manufacturers pay much attention to the development of keyboard devices.
Hereinafter, the configurations and functions of a conventional keyboard device will be illustrated with reference to FIG. 1. FIG. 1 is a schematic view illustrating the outward appearance of a conventional keyboard device. As shown in FIG. 1, plural keys 10 are exposed to a surface of the conventional keyboard device 1. When one of the plural keys 10 is depressed by the user's finger, a corresponding signal is issued to the computer, and thus the computer executes a command corresponding to the depressed key.
With increasing development of science and technology, a tablet personal computer is introduced into the market. The tablet personal computer has slim and small-sized appearance similar to a LCD screen. In addition, the display screen of the tablet personal computer is a touch screen. Via the touch screen, the user may input commands to the tablet personal computer in order to control operations of the tablet personal computer. In case that the user wants to input characters or symbols into the tablet personal computer, an on-screen keyboard is enabled and shown on the touch screen of the tablet personal computer. The on-screen keyboard is a virtual keyboard simulating the real keyboard device. By touching icons of the on-screen keyboard, corresponding characters or symbols are inputted into the tablet personal computer. In other words, characters or symbols may be directly inputted into the tablet personal computer without the need of using any external keyboard device.
Although the on-screen keyboard simulating the real keyboard device may be shown on the tablet personal computer and it is not necessary to use an external keyboard device to input characters or symbols, there are still some drawbacks. For example, since the tablet personal computer has the small-sized and slim appearance, the size of the touch screen of the tablet personal computer is about 9.7 inches. Due to the limitation of the size of the touch screen, the on-screen keyboard shown on the touch screen is much smaller than the real keyboard device. Since the on-screen keyboard is too small and the icons of the on-screen keyboard are crowded, the possibility of erroneously touching other icons during the process of operating the on-screen keyboard will be increased. Consequently, in many circumstances, the user prefers using an additional external keyboard device that has functions and configurations similar to the keyboard device as shown in FIG. 1. After the external keyboard device is in communication with the tablet personal computer, the user may input characters or symbols via the external keyboard device. However, after the external keyboard device is in communication with the tablet personal computer, the tablet personal computer should be placed and supported on a prop stand (e.g. a bookshelf). Meanwhile, the tablet personal computer is considered as a general display screen, and the external keyboard device is used for inputting characters or symbols. Generally, the external keyboard device is connected with the tablet personal computer via a universal serial bus (USB).
From the above discussions, the use of the external keyboard device may facilitate the user to operate the tablet personal computer according to the usual practice of the user. However, for allowing the user to view the touch screen of the tablet personal computer, the tablet personal computer should be placed on the prop stand in order to be in an upright status or an inclined status. Consequently, a keyboard device for a tablet personal computer and with a supporting function has been disclosed.
FIG. 2 is a schematic perspective view illustrating a conventional keyboard device for a tablet personal computer and with a supporting function. As shown in FIG. 2, the keyboard device 2 comprises a base 20, and upper cover 21, and plural keys 22. The upper cover 21 is connected with the base 20, and rotatable relative to the base 20. Consequently, the keyboard device 2 may be selectively in a folded status or a supporting status. In case that the keyboard device 2 is in the folded status, the base 20 is covered by the upper cover 21, so that the keyboard device 2 is shaped as a rectangular slab. In case that the keyboard device 2 is in the supporting status, a first included angle A1 is formed between the upper cover 21 and the base 20. Meanwhile, a tablet personal computer 23 may be placed on the base 20 and supported by the upper cover 21. The plural keys 22 are disposed on the base 20. When the plural keys 22 are depressed by the user, corresponding key signals are generated and issued to the tablet personal computer 23. The upper cover 21 has a foldable plate 211. The foldable plate 211 is foldable relative to the upper cover 21. Consequently, the foldable plate 211 is in parallel with the upper cover 21, or a second included angle A2 is formed between the foldable plate 211 and the upper cover 21. Moreover, the base 20 has a prop tray 201. The prop tray 201 is stored within the base 20. The prop tray 201 has plural stopping ribs 2011. The plural stopping ribs 2011 are protruded upwardly from a surface of the prop tray 201. In case that the keyboard device 2 is in the supporting status, the plural keys 22 are exposed, the prop tray 201 is pulled out from the base 20, and the foldable plate 211 is folded relative to the upper cover 21 to be contacted with the prop tray 201. The stopping ribs 2011 of the prop tray 201 are used for stopping the foldable plate 211 in order to support the upper cover 21. As shown in FIG. 2, the foldable plate 211 is stopped by one of the stopping ribs 2011, and the tablet personal computer 23 on the base 20 is supported by the upper cover 21 in an inclined status. Under this circumstance, a touch screen 231 of the tablet personal computer 23 may be viewed by the user, and the exposed keys 22 may be used to input characters or symbols.
In the keyboard device 2, the size of the upper cover 21 is substantially identical to the size of the base 20, and the size of the upper cover 21 is slightly larger than the size of the tablet personal computer 23. For example, if the touch screen 231 of the tablet personal computer 23 is about 9.7 inches, the size of the upper cover 21 and the size of the base 20 are slightly larger than 9.7 inches. Moreover, the plural keys 22 should be disposed on the base 20 that has the above-mentioned size. Due to the size limitation, the sizes of the plural keys 22 are smaller than the sizes of the plural keys 10 of the conventional keyboard device 1, but the sizes of the plural keys 22 are still larger than the plural icons shown on the touch screen 231. Consequently, the plural keys 22 on the base 20 can be normally operated by the user.
Recently, the general trends in designing electronic devices are toward small size, light weightiness and easy portability. Consequently, a small size tablet personal computer has been introduced into the market. For example, the size of the touch screen of the small size tablet personal computer is about 7 inches. Since the size of the on-screen keyboard shown on the 7-in touch screen of the small size tablet personal computer is smaller than the size of the on-screen keyboard shown on the 9.7-in touch screen of the tablet personal computer, the use of the small size tablet personal computer becomes hindrance from touching the plural icons of the on-screen keyboard. In case that the above keyboard device 2 for the tablet personal computer is applied to the small size tablet personal computer, the sizes of the upper cover 21 and the base 20 should be correspondingly scaled down. That is, the sizes of the plural keys 22 are correspondingly reduced. Under this circumstance, the possibility of erroneously touching other keys and the possibility of erroneously inputting characters or symbols will be increased.
Therefore, there is a need of providing a keyboard device for a small size tablet personal computer in order to reduce the possibility of erroneously touching other keys.